Strophanthidin-sensitive components of potassium and sodium movements in skeletal muscle as influenced by the internal sodium concentration.
"Low sodium" muscles were prepared which contained around 5 mmoles/kg fiber of intracellular sodium. "High sodium" muscles containing between 15 and 30 mmoles/kg fiber of intracellular sodium were also prepared. In low sodium muscles application of 10(-5)M strophanthidin reduced potassium influx by about 5%. Potassium efflux was unaffected by strophanthidin under these conditions. In high sodium muscles, 10(-5)M strophanthidin reduced potassium influx by 45% and increased potassium efflux by 70%, on the average. In low sodium muscles sodium efflux was reduced by 25% during application of 10(-5)M strophanthidin while in high sodium muscles similarly treated, sodium efflux was reduced by about 60%. Low sodium muscles showed a large reduction in sodium efflux when sodium ions in the Ringer solution were replaced by lithium ions. The average reduction in sodium efflux was 4.5-fold. Of the amount of sodium efflux remaining in lithium. Ringer's solution, 40% could be inhibited by application of 10(-5)M strophanthidin. The total sodium efflux from low sodium muscles exposed to Ringer's solution in which lithium had been substituted for sodium ions for a period of 1 hr can be fractionated as 78% Na-for-Na interchange, 10% strophanthidin-sensitive sodium pump, and 12% residual sodium efflux. It is concluded that large strophanthidin-sensitive components of sodium and potassium flux can be expected only at elevated sodium concentrations within the muscle cells.
D000818:Animals; D001001:Anura; D001693:Biological Transport, Active / Q000187:drug effects*; D002297:Cardanolides / Q000494:pharmacology*; D008094:Lithium / Q000494:pharmacology; D009132:Muscles / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D010783:Photometry; D011188:Potassium / Q000378:metabolism*; D011194:Potassium Isotopes; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D012975:Sodium Isotopes
D002297:Cardanolides; D011194:Potassium Isotopes; D012975:Sodium Isotopes; D010042:Ouabain; D008094:Lithium; D012964:Sodium; D011188:Potassium